1. Field of the Invention
The present invention generally relates to controlling an operation of various types of gas discharge lamps. The present invention specifically relates to an improvement in the operational performance of electronic ballast within a high frequency range of a gas discharge lamp.
2. Description of the Related Art
A high intensity discharge (xe2x80x9cHIDxe2x80x9d) gas discharge lamps as known in the art suffer from acoustic resonances when such lamps are operated within a high frequency HF operation between a few kHz and hundreds of kHz, depending on the type of lamp. However, the acoustic resonances significantly weaken within such gas discharge lamps whereby the acoustic resonance do not have negative affect on the performance of the gas discharge lamp when the gas discharge lamps are operated within a very high frequency operation that is above the highest acoustic resonance (e.g., 150 kHz for a 400 W MH lamp). A consequence of operating the gas discharge lamp in the VHF operation is a generation of electromagnetic interference. Additionally, when a gas discharge lamp is operated at HF lamp current, the electrode temperature modulation (i.e., difference in anode and cathode temperatures) will vanish. This results in a different electrode operating conditions, which could cause changes in the arc attachment on the electrode. Arc instabilities related with arc-electrode attachment have been found when 400 W MH lamps are operated on high frequencies even up to as high as 500 kHz. Also, large coil differences between individual lamps are also found when lamps are operated on high frequencies.
Back-arcing of a gas discharge lamp involves an arc attachment of the arc on the back of the electrode coil of the lamp as opposed to an ideal arc attachment of the arc on the tip of the electrode. This can affect thermal balance of the end of the arc tube, which in turn can affect the vapor pressures. Consequently, the color properties of the lamp are affected. Currently, related prior art has failed to address back-arcing.
The present invention addresses the shortcomings of the prior art.
The present invention relates to an improved high frequency ballast. Various aspects of the present invention are novel, non-obvious, and provide various advantages. While the actual nature of the present invention covered herein can only be determined with reference to the claims appended hereto, certain features, which are characteristic of the embodiments disclosed herein, are described briefly as follows.
One form of the present invention is a first method of operating a half-bridge coupled to a gas discharge lamp. First, the half-bridge is operated to establish an operating frequency of a lamp current above all acoustic resonances within a high frequency operation range of the gas discharge lamp. Second, the half-bridge is operated to apply a frequency modulation to the operating frequency.
A second form of the present invention is a second method of operating a half-bridge coupled to a gas discharge lamp. First, the half-bridge is operated to establish an operating frequency of a lamp current. Second, the half-bridge is operated to apply an amplitude modulation to the lamp current in response to a reception by the half-bridge of a drive voltage having a waveform.
A third form of the present invention is a third method of operating a half-bridge coupled to a gas discharge lamp. First, the half-bridge is operated to establish an operating frequency of a lamp current above all acoustic resonances within a high frequency operation range of the gas discharge lamp. Second, the half-bridge is operated to apply a frequency modulation to the operating frequency. Finally, the half-bridge is operated to apply an amplitude modulation to the lamp current in response to a reception by the half-bridge of a drive voltage having a waveform.
A fourth form of the present invention is a fourth method of operating a half-bridge coupled to a gas discharge lamp. First, the half-bridge is operated to provide a lamp current to the lamp during a start-up operation of the gas discharge lamp. Second, the half-bridge is operated to establish the lamp current at an operating ampere level during an arc heating phase of the gas discharge lamp. The operating ampere level is equal to or greater than a minimum run-up ampere level to thereby impede any back-arcing within the gas discharge lamp whereby the gas discharge lamp substantially achieves a color specification for the gas discharge lamp.
The foregoing forms and other forms, features and advantages of the present invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the present invention rather than limiting, the scope of the present invention being defined by the appended claims and equivalents thereof.